Process for valorizing liquid manure from pigs and device for implementing such methods

ABSTRACT

The present invention relates to a method for valorizing liquid manure from pigs by elaboration of biological amendments, said method comprising the fermentation of a biomass based on a mixture of pig liquid manure and a carbonaceous medium. Said biomass is seeded by a bacterial selection comprising Serratia and Klabsiella also relates to a device for implementing such method.

The present invention has for its object a process for valorizing liquidpig manure and a device for carrying it out.

The process according to the invention allows, from said liquid pigmanure, the elaboration of biological improvements, usable inagriculture.

Liquid pig manure is, per se, a very rich fertilizer.

However, its use, crude--application as such or after atomization--isnot without danger for the earth and groundwater tables.

In fact, liquid pig manures contain, on the one hand, pathogenicbacteria and, on the other hand, polluting substances such as nitrites,nitrates, copper . . . In addition, they disengage a most unpleasantodour.

According to the invention, a process is proposed which makes itpossible, on the one hand, to neutralize the detrimental effects of theliquid manure set forth hereinabove, and, on the other hand, to valorizeit by transforming it into a compost able to be used like any organiccompost.

Such transformation may be carried out, according to the invention, in asurprizingly short time.

Such results are obtained by the fermentation of a biomass based on amixture of liquid pig manure and a carbon-containing support underparticular conditions.

The process according to the invention employs for the fermentation aspecific bacterial selection. It is advantageously carried out to ensureoptimal working conditions for the bacteria of this selection.

According to the invention, the biomass--liquid manure+carbon-containingsupport--is seeded by a bacterial selection including Serratia andFlebsiella.

These bacteria belong to the family of Enterobacteriaceae, they are 100%Gram⁻.

They were chosen for their intrinsic properties, but haveproved--combined--of surprizingly high-performance, both at the level ofthe course of the process of the invention, and at the level of the useof the product obtained by this process.

It is question of reversible bacteria, capable of working both in anaerobic medium and in an anaerobic medium. They attack the organicmatter and are in particular capable of reducing the nitrates intogaseous nitrogen.

In addition, they present a thermal resistance which allows them to beused towards 70° C.

The biomass, treated in accordance with the process of the invention,must be subjected to such temperatures (up to 72° C.) in order, on theone hand, to remove the pathogenic bacteria from the liquid manure and,on the other hand, to start the process of humification of at least apart of the carbon-containing support.

According to the invention, this pair of bacteria has therefore beenselected.

They are available on the market. They may act, in accordance withvariants of the invention, in combination with others, but prove to beof sufficiently high performance by themselves.

They advantageously act in equal quantities.

The biomass to be seeded, according to the process of the invention, is,as specified hereinabove, based on a mixture of liquid pig manure and acarbon-containing support.

The manure is a liquid, disengaging a sickening smell and generallycomprising from 12 to 15% of dry matter.

According to a preferred variant of the process of the invention, it isplaced in suspension before being mixed with the carbon-containingsupport. A colloidal is employed for flocculation thereof.

This colloidal or flocculant ensures suspension of the solid particlesand imprisons, traps, retains the odour.

It may be selected for example from among the alginates,carboxymethylcellulose, beer yeast, rice starch, Indian corn starch, . ..

A natural colloidal will advantageously be chosen, which will constitutea reserve of nourishment for the bacteria, upon use thereof (awakening)in the soils.

Burst Indian corn starch is preferred since it is question of a naturalcolloidal, relatively inexpensive and which acts at ambient temperature.

The use of non-burst corn starch would involve heating the liquid manuretowards 40°-45° C.

The liquid manure, advantageously flocculated --which is then in theform of a slimy liquid whose odour has virtually disappeared--is mixedbefore seeding with a carbon-containing support.

The mixture contains from 55 to 65% by weight of liquid manure--with12-15% dry matter--for 35 to 45% by weight of carbon-containing support.

The carbon-containing support is generally based on straw. Any type ofstraw may be used: straw proper, Indian corn straw, hay, even treebranches, . . .

Said carbon-containing support may consist solely of said straw. It mayalso consist of a mixture of straw and green wood sawdust, for example.

The mixture--liquid manure, carbon-containing support - may constitutethe raw material--biomass --necessary for carrying out the process ofthe invention. However, for the elaboration of high-performancebiological improvements, other raw materials ensuring a supply ofmineral substances, in A-P-K, will advantageously be employed in theprocess of the invention.

According to the invention, these other raw materials, which ensure inparticular the addition of phosphates, potash, are used before seeding.In this way, said raw materials will be integrated, fixed by thebacteria to the carbon-containing support, particularly the straw. Thework of said bacteria renders these materials non-leachable.

These raw materials, incorporated before seeding, must, however, nothinder the work of the bacteria, particularly by modifying the pH of themedium. This is why only natural products are used in the processaccording to the invention.

Such products advantageously consist of:

fine building plaster (A): said plaster is polyvalent. It acts both atthe level of manufacture of the improvement and at the level of its usein the soils. It performs functions of binding, slow-release, . . . Italso contributes to the imprisonment of the odour of the liquid manure;

calcined natural phosphate (P);

natural potash (K);

calcium carbonate, preferably with magnesium.

In this way, according to a preferred variant of the invention, finebuilding plaster, calcined natural phosphate, natural potash, andcalcium carbonate, preferably with magnesium are distributed within thecarbon-containing support, before its mixture with the liquid manure:these four products being used in equal quantities, their total quantityrepresenting from 10 to 25% by weight of the liquidmanure/carbon-containing support mixture.

According to another variant, these four products may be added to theliquid manure/carbon-containing support mixture previously made.

The biomass thus obtaine--liquid manure carbon-containingsupport+possibly mineral substances--is, according to the invention,subjected to a heat treatment before its seeding. It is taken to about70° C.

Such heat treatment ensures concentration of the liquid manure, thepartial drying of the biomass before its seeding and begins to destroythe pathogenic bacteria that it contains.

The rate of humidity of the biomass obtained must be close to 40%--38 to43%.

Such a humidity rate of the biomass allows, in the course offermentation, optimum work of the bacteria.

The biomass is seeded with Serratia and Klebsiella in aqueous solution,by pulverization.

The lyophilized bacteria are on supports, for example at a rate of 6.610⁸ germs/gram. About 200 to 300 g of such supports are introduced for aton of biomass with 40% humidity. The use of a greater quantity ofbacteria is not detrimental.

In the course of incubation, the temperature of the biomass attains 72°C. The pathogenic bacteria of the liquid manure do not withstand thistemperature.

When, in the course of incubation, the biomass redescends in mesophilicphase, it is oxygenated. It is only sequentially oxygenated for a shortinstant.

Incubation must last for a sufficiently long period to kill all thepathogenic bacteria, to humify somewhat the carbon-containing support.However, it must not create losses of proteins.

The process of the invention allows an interesting biomass to beobtained after 10 to 15 days. After 12 days, it is generally of optimalquality.

This result is particularly surprizing since the elaboration of organicfertilizers generally takes much more time.

The living biomass obtained is advantageously directed, according to theprocess of the invention, towards a pressure granulator. This treatmentmakes it possible to deaden the bacteria and to obtain a product whichis easier to store and distribute in the earth.

Compression is to be carried out on the biomass at about 15-18%humidity. After 10-15 days of incubation of the biomass at 40% humidity,such a biomass is obtained. By exerting 70 to 80 bars thereon, theexpected result is obtained without superfluous heating. In fact, it issuitable not to kill the bacteria by taking the biomass by compressionto an excessive temperature.

The biomass is then obtained in the form of granules. Distributed in thesoil, these granules disintegrate. The deadened bacteria then awaken andbegin to work.

According to the invention, a process is therefore proposed which, froma very pollutant product --liquid pig manure--allows the elaboration ofa living improvement, which is rich (presenting a valid N-P-K) andnon-leachable.

Said improvement is bereft of harmful microbes, it is alsoadvantageously odour-free.

These results are obtained thanks to the intervention of specificbacteria.

According to another object of the present invention, a device isproposed for carrying out the process described hereinabove.

This device comprises:

mixer, supplied, on the one hand, with flocculated liquid manure and, onthe other hand, with carbon-containing support;

a fluidized bed drier, advantageously provided with a device forrecovering the fines, for subjecting the mixture--liquid manure,carbon-containing support--to a heat treatment;

an enclosure for pulverization of a solution containing the bacteria onthe mixture;

reactors or locations for fermentation provided with an oxygenationdevice;

a rotary granulating press.

At the level of the mixer, the natural products ensuring supply ofphosphate, potash . . . advantageously act.

Such a device allows the process according to the invention to becarried out and therefore a biological improvement, which is rich,odour-free, non-leachable, clean (free of pathogenic bacteria), to beobtained in a very short time.

Other characteristics and advantages of the invention will be morereadily understood on reading the following description and withreference to the accompanying single FIGURE, which schematically shows adevice for carrying out the process according to the invention.

In the liquid manure tank (1)is prepared a suspension of liquid pigmanure. The liquid manure containing between 12 and 15% dry extract issupplied at (1'), and, at (1"), burst Indian corn starch. A suspensionof said liquid manure may thus be obtained at ambient temperature.

The carbon-containing support is stored at (4) and, at (5), thesupplement of natural substances which it is desired to incorporate inthe mixture to be composted. More precisely, straw is stored at (4'),green wood sawdust at (4") and, at (5), an equal-part mixture of finebuilding plaster, calcined natural phosphate from Senegal, naturalpotash (patenkali) and magnesium calcium carbonate.

At (6), the straw is broken up.

At (7) has been schematically shown a weighing hopper allowingelaboration of the mixture: straw, sawdust, natural supplement, moreprecisely the elaboration of the desired quantity of carbon-containingsupport enriched with APK.

Said enriched carbon-containing support is, thanks to the supplier (9)introduced in the vertical mixer (3) to be mixed with the flocculatedliquid manure, itself supplied via pump (2).

By way of example, it may be indicated that 600 l of liquid manureplaced in suspension by addition therein of 3 kg of burst Indian cornstarch, are mixed with:

400 kg of carbon-containing support constituted by about 320 kg of straw(80%) and 80 kg of green wood sawdust (20%); and

200 kg of supply of APK.

The homogeneous mixture obtained is directed towards a fluidized beddrier (10). At (10') is schematically shown the hot air inlet. Insidethe drier (10), 3 temperature zones are distinguished: the first atabout 70° C., the second at about 60° C., the third towards 35°-40° C.The parameters of heating are determined so that, on leaving said drier,the final product is at about 40% humidity. In the course of this heattreatment, the liquid manure is concentrated and the pathogenic bacteriathat it contains are destroyed. (11) schematically represents a devicefor recovering the fines; (12), a conveyor belt equipped with a weighinghopper.

The mixture at 40% humidity is seeded in the enclosure (16) forbacterial retention.

The bacterial selection (13') is diluted in water (13") at 33°-35° C. in(13). The bacterial liquid is stored in (14). At (15), its pulverizationdevice has been schematically shown.

The intervening quantities are specified by way of example: 250 g oflyophilized bacteria with their support, diluted in 5 1 of water, areprovided for a mass of one ton (1000 kg of product at 40% humidity). Onsaid support (sawdust+proteins) are found about 6.6 10⁸ germs/gram.

The seeded mixture is directed at (17) towards reactors or windrows (18)(longitudinal pile having a width of about 1 m and a height of 80 cm).

These reactors or windrows (18) are equipped with an oxygenation device(20) supplied at (19) by a mixture of oxygen and air, heated to 35° C.

Oxygenation takes place for a duration of 2 minutes whenever the biomassdescends in mesophilic phase (38°-33° C.).

Incubation of the biomass takes place as follows: in about 8 to 9 hours,it rises in thermophilic phase (at an outside temperature of 15° to 18°C., the temperature within the biomass varies between 60° and 72° C.).This thermophilic phase lasts between 48 to 72 hours. The biomass thenbegins to descend in mesophilic phase and it is then that oxydationtakes place.

As soon as oxygenation is finished, the biomass rises in thermophilicphase . . . etc . . .

The duration of incubation of the biomass has been limited to 12 days.

After this time, the biomass--which is living --is directed towards apressure granulator: rotary granulating press. The bacteria are deadenedby compression to about 70-80 bars. Small granules are obtained whichmay easily be stored and easily distributed in the earth.

The organic fertilizer thus obtained in a very short time (12 to 15days) from liquid pig manure, has no more odour, contains no morepathogenic bacteria and proves to be of particularly high-performance.In fact, it presents a valid N-P-K, capable of being used at best assaid fertilizer is not leachable.

The results of an analysis on the faecal contamination indicator germsand the total microflora, are proposed hereinbelow:

                  TABLE 1                                                         ______________________________________                                        Analytic results concerning the search for                                    faecal contamination indicator germs                                          and the total microflora                                                                   Liquid manure                                                                            Final product                                         ______________________________________                                        Faecal coliforms                                                                             1.65 · 10.sup.8 /l                                                                not detected                                      (E.c.)                                                                        Faecal streptococci                                                                          5.5 · 10.sup.8 /l                                                                 4.8 · 10.sup.3                           Total microflora                                                                             6 · 10.sup.9 /l                                                                   1.32 · 10.sup.11                         ______________________________________                                    

After only 12 days, all the faecal coliforms disappeared and the densityof the faecal streptococci is reduced by a factor 6. This result isremarkable as it allows the powder to be applied after only aboutfifteen days. The increase in temperature during the fermetationprocesses is probably the cause of this mortality of the bacteria of thefaecal contamination. On the other hand, the total microflora isconsiderably multiplied thanks to the organic compounds of the mixtureattesting the placing of a living biomass.

The organic fertilizer obtained according to the invention may serve forthe fertilization of arid soils, for the regeneration of soils exhaustedeither by intensive crop-growing or by excessive or simply prolonged useof synthetic fertilizers.

What is claimed is:
 1. Process for valorizing liquid pig manure byelaboration of biological improvements, said process comprising therfermentation of a biomass based on a mixture of liquid pig manure and acarbon-containing support, characterized in that said biomass is seededby a bacterial selection consisting essentially of a mixture of Serratiaand Klebsiella in equal quantity, said mixture present in an amountsufficient to provide a thermophilic phase fermentation temperature ofbetween 60° C. and 72° C.
 2. Process according to claim 1 characterizedin that said biomass is elaborated from a mixture of the liquid manureplaced in suspension by addition therein of a natural flocculent and thecarbon-containing support.
 3. Process according to claim 2,characterized in that burst Indian corn starch is used for placing theliquid manure in suspension.
 4. Process according to claim 1characterized in that said mixture contains from 55 to 65% by weight ofa liquid manure with 12-15% of dry matter, placed in suspension, andfrom 35 to 45% by weight of carbon-containing support.
 5. Processaccording to claim 1 characterized in that the carbon-containing supportis based on straw.
 6. Process according to claim 1 characterized in thatthe biomass contains, in addition to the liquid manure and thecarbon-containing support, natural products ensuring a supply of mineralsubstances.
 7. Process according to claim 6, characterized in that thereis distributed within said carbon-containing support, before it is mixedwith the liquid manure, a material selected from the group consisting offine building plaster, calcined natural phosphate, natural potash andcalcium carbonate with or without, preferably with magnesium, in equalquantities, the whole representing from 10 to 25% by weight of theliquid manure--carbon-containing support mixture.
 8. Process accordingto claim 1 characterized in that seeding is effected by pulverization ofan aqueous solution containing the bacteria, on the biomass with about40% humidity.
 9. Process according to claim 1 characterized in that,before its seeding, the biomass is subjected to a heat treatment, ataround 70° C., to lower its rate of humidity to about 40%.
 10. Processaccording to claim 9 characterized in that, during its heat treatment,the biomass is sequentially oxygenated.
 11. Process according to claim 9characterized in that after heat treatment, said biomass is granulatedunder pressure.
 12. The process according to claim 1, characterized inthat said amount of Serratia and Klebsiella is an amount sufficient toraise the temperature of said biomass to about 70° C.
 13. Processaccording to claim 5 characterized in that the straw is in admixturewith green wood sawdust.